Two l‑Proline Cadmium Thiocyanates\nwith Moderate Second-Harmonic-Generation Responses and Large Birefringences

Two organic–inorganic cadmium thiocyanates, namely,\nCd(SCN)(l-C<sub>5</sub>H<sub>8</sub>NO<sub>2</sub>) (<b>1</b>)\nand Cd(SCN)<sub>2</sub>(l-C<sub>5</sub>H<sub>9</sub>NO<sub>2</sub>) (<b>2</b>), have been synthesized using l-proline as the bridging ligand. The two compounds have double-chain-like\nand layered structures, respectively. They feature moderate second-harmonic-generation\nresponses (0.33 × KH<sub>2</sub>PO<sub>4</sub> for <b>1</b> and 1.58 × KH<sub>2</sub>PO<sub>4</sub> for <b>2</b>),\nwide band gaps (4.68 eV for <b>1</b> and 4.59 eV for <b>2</b>), and large birefringences (0.210 at 546 nm for <b>1</b> and\n0.295 at 546 nm for <b>2</b>). The structure–property\nrelationship was explicated by first-principle calculations based\non density functional theory.